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Motivation Real-time systems: time critical systems Real-time systems: time critical systems Schedule: assignment of jobs to available processors Schedule: assignment of jobs to available processors Feasible schedule: every job completes by its deadline Feasible schedule: every job completes by its deadline Scheduling algorithms: Scheduling algorithms: Clock driven / Round-robin /Priority-driven Clock driven / Round-robin /Priority-driven Need a tool to illustrate how these algorithms work Need a tool to illustrate how these algorithms work Particularly in RTS classes Particularly in RTS classes and find feasible schedules and find feasible schedules Helpful for research Helpful for research

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Algorithm Overview: EDF Earliest Deadline First (EDF) Earliest Deadline First (EDF) Dynamic priority scheduler Dynamic priority scheduler Highest priority is assigned to the task with the nearest deadline Highest priority is assigned to the task with the nearest deadline Advantages Advantages EDF theoretically superior to DM EDF theoretically superior to DM Guaranteed scheduleability if CPU utilization 100% or less Guaranteed scheduleability if CPU utilization 100% or less Disadvantages Disadvantages More difficult to implement More difficult to implement Higher system overhead Higher system overhead Overloaded system is unpredictable (non-critical tasks may be scheduled before critical tasks) Overloaded system is unpredictable (non-critical tasks may be scheduled before critical tasks)

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Algorithm Overview: LSTF (bonus!) Least Slack Time First (LSTF) Least Slack Time First (LSTF) Dynamic priority scheduler Dynamic priority scheduler Highest priority given to the task with the least slack time (timeToDeadline – executionTimeLeft) Highest priority given to the task with the least slack time (timeToDeadline – executionTimeLeft) Advantages Advantages Same as EDF Same as EDF Intuitively logical Intuitively logical Disadvantages Disadvantages Same as EDF Same as EDF